The primary objective of this study is to evaluate the safety of NPS 1506 when administered to subjects with acute ischemic stroke. The range of well tolerated doses will be identified. The secondary objectives to this study are: 1)To evaluate the pharmacokinetics of NPS 1506 and its major metabolite, NPS 846 when administered to subject with acute ischemic stroke. 2)As appropriate, to correlate plasma concentrations with observed pharmacologic and/or toxic effects. 3)To pilot the use of selected clinical outcome measures.